The present invention relates to a process for the treatment of plant or vegetable material, pretreatment by pressing leading to the obtaining of a liquid phase and a solid phase from the plant material, said phase being further processed separately, as well as to an apparatus for performing this process.
It is known to work up plant material in such a way that the minimum quantity of nutrients contained therein is lost. In view of the careful treatment required, thermal or chemical processes are unusable, so that it is merely possible to employ a mechanical process, in which the breaking down of the cells takes place by pressing, linked with a crushing, scraping or abrading treatment. If a time between the harvest of the material or crop and its processing is short, this process can be considered to constitute an optimum, because it is also possible to prevent mold formation through a germicidal treatment. Further processing of the liquid phase makes it possible to extract the protein contained therein, which can be used in many different ways for feeding humans and animals. The remaining liquid residue is removed from the solid phase and is simultaneously preserved. As the thus obtained product still has a high protein content, it is best used as an albumin carrier in animal food.
In a known process (EP 108 762), the solid and liquid phases are obtained by a pressing treatment of the plant material. In particular, the use of screw presses is proposed, because in order to protect the nutrients contained in the plant material, it is only possible to use a mechanical preparation and not a thermal or chemical preparation. The purpose of this preparation is to open or destroy the protective coatings of the plant cells by an intense crushing, scraping and abrading treatment of the plant material, so that a liquid phase consisting of cell sap and a solid phase essentially consisting of plant fibers are obtained. This process can be used for processing plant materials of different origins, but the separation process, as it essentially consists of a single pressing treatment and consequently takes place in a single pressing means, cannot be adjusted in an optimum manner to the different plant crops.
A known pressing means (EP 108 763) is constructed as a twin-screw press or extruder comprising a plurality of casing elements simultaneously defining treatment sections, in which the plant material is successively treated until at the outlet side the solid phase is discharged as a dry substance, usually in pellet form. The resulting liquid phase is pumped out or is sucked off after being converted into a vaporous phase. Thus, such a press brings about the separation of the two aforementioned phases. Through the arrangement of the screw press in successive, lined up sections, the corresponding screw section can admittedly be adapted to the change of the product being pressed, but this adaptation is not of an optimum nature, because on the one hand the speed is the same for all the processing sections and on the other it is substantially impossible to carry out a check and then control the material being pressed due to the directly succeeding treatment sections.